The Laws of Nature
During the making of the constitution of a nation, certain laws of the state are made. But unless there are some authorities to carry out and protect them, those laws have no meaning. Similarly the Lord has created certain laws of nature, and are executed at every step by a law maker. For every action there is an equal corresponding reaction. This is a law of nature. Although this is the law, karma means that according to how you live your life, there will be a certain state of consciousness, a certain thought at the time of death, and according to the nature of that thought you will be carried to the next body. At the time of death, a living being is carried by his subtle body to another gross body. Higher authorities decide what kind of gross body the living entity will have according to the way he has lived his life. - HH Radhanath Swami.